#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
#include<cmath>
using namespace std;
int cnt;
long long sum;
int main()
{
	int x;
	while (cin >> x)
	{
		cnt++;
		sum += x;
	}
	for (int i = 0; i < cnt-1; i++)
	{
		sum *= 2;
	}
	cout << sum << endl;
	return 0;
}